Transition Metal Imido Compounds as Ziegler–Natta Olefin Polymerisation Catalysts

Transition metal imido compounds having the general formula [(L)nM(NR)] [where (L)n is a supporting ligand or ligand set, and R typically is alkyl or aryl] have been known for nearly 50 years, and during the last two decades have been the focus of considerable attention. Relatively recently their potential application in the Ziegler–Natta polymerisation of olefins has been realised. In this contribution we review the Ziegler–Natta polymerisation of olefins by transition metal imido compounds. A general introduction to homogeneous Ziegler–Natta olefin polymerisation and key aspects of transition metal imido chemistry is given, followed by a short description of a related imido-based polymerisation process, namely ring-opening olefin metathesis polymerisation catalysed by imido-supported molybdenum and tungsten alkylidenes. A summary of the “design principles” that have been employed in the development of certain imido-based Ziegler–Natta catalysts is presented, followed by a comprehensive survey of the literature in the title area.